ValueError: Could not process parameters in Python/MySQL

Question

I want to prevent duplicate usernames when people register.

Here is my code snippet:

def submit(self):
    username_info = username.get()
    username_password = password.get()
  
    #connect to db
    db = mysql.connector.connect(host = 'localhost', user = 'root', password = '', database = 'user')

    #create a cursor
    mycursor = db.cursor()
    #insert to db
    sql = ("INSERT INTO useraccess (user_type, password) VALUES (%s, %s)")

    query = (username_info, username_password)
    mycursor.execute(sql, query)
    #commit
    db.commit()

    #create a messagebox
    messagebox.showinfo("Registration", "Successfully Register")

    #if username has been used
    find_user = ("SELECT * FROM useraccess WHERE user_type = ?")
    user_query = (username_info)

    mycursor.execute(find_user, user_query)
    #if (username == username_info):
    if mycursor.fetchall():
        messagebox.showerror("Registration", "The username chosen is already used. Please select another username")
    else:
        messagebox.showinfo("Registration", "Account Created!")
    

But every time I run it, although the username has been registered in the db, it only shows the successfully created messagebox and error:

ValueError: Could not process parameters.

Anyone can help me to solve this problem?

Answer 1

I believe the source of the problem is in the line

user_query = (username_info)

It should be

user_query = (username_info,)

The trailing comma is the syntactic difference between an expression in parentheses and a tuple.

Another issue with code is the query:

find_user = ("SELECT * FROM useraccess WHERE user_type = ?")

Which should be:

find_user = ("SELECT * FROM useraccess WHERE user_type = %s")